code: def test_div0(self) -> None:
      summarizer = Summarizer([Var(), Mean()])
      summ = summarizer.summary
      self.assertIsNone(summ)
  
      summarizer.update(torch.tensor(10))
      summ = summarizer.summary
      assertTensorAlmostEqual(self, summ["mean"], 10)
      assertTensorAlmostEqual(self, summ["variance"], 0)
  
      summarizer.update(torch.tensor(10))
      summ = summarizer.summary
      assertTensorAlmostEqual(self, summ["mean"], 10)
      assertTensorAlmostEqual(self, summ["variance"], 0)
  
file_path: captum/tests/attr/test_stat.py
imports: import random
  import torch
  from captum.attr import Max, Mean, Min, MSE, StdDev, Sum, Summarizer, Var
  from tests.helpers.basic import assertTensorAlmostEqual, BaseTest
label_desc: Use image node_id 1 for calling the Test obj's underlying member method code with example usage: obj.test_div0() without return types